This invention relates to well cleaning apparatus and finds a particular application in the cleaning of stepped regions of well bores such as the well head.
Bore holes are typically lined with a concrete casing. In order to maximise production from the well it is necessary to clean out the casing, removing debris and contaminants.
One region of the bore hole which is particularly hard to clean is the well head. The well head is stepped in diameter, with a larger diameter at the top. Due to this stepped profile, tools adapted to clean the main body of the bore hole with brushes or jets of cleaning fluid will not be of the correct diameter to efficiently clean the upper steps. At the present time, the stepped profile of the well head is generally not sufficiently cleaned in consequence to a lack of satisfactory equipment. It is recognised in the present invention that the more efficient cleaning of this stepped region of the well head would significantly improve fluid flow in that area and so have benefits for production.
In the art it is known to jet well fluid against the well casing to perform a cleaning function. Tools adapted for this purpose are often called circulation tools. Such tools typically have a body member with an axial bore therethrough to permit circulation and one or more fluid ports which extend radially through side walls of the body member. Means are provided for controlling the flow path of fluid between a path running axially through the tool and a path leading to the radial outlets.
However, as discussed above, in the past such tools have been designed with tool bodies of a constant outer diameter and therefore have not been suitably adapted for use in well head cleaning.
Moreover, circulation tools used in well bore cleaning known heretofore are limited by the pressure head of fluid pumped through the tool. Typically, circulation tools are adapted to be connected to a work string or the like and thus their ability to jet fluid in a radial direction against the inside casing wall is affected by the pressure and volume of fluid pumped through the string.
It will be appreciated by those skilled in the art that it would be advantageous if the pressure and/or velocity of expelled fluid through radial outlets could be increased without the need to make increased demands on the pumping equipment.
It is therefore a further object of the present invention to provide a greater capacity or ability to meet these advantages and overcome or mitigate any aforementioned disadvantages associated with the prior art.
According to the present invention there is provided a clean up tool for use in a well bore, the tool comprising a tool body defining a first and second liquid passage which each communicate with a venturi chamber, wherein the first and second liquid passages are each associated with an inlet for receiving well fluid into the tool, wherein the tool body further comprises a discharge passage associated with one or more outlets, wherein the discharge passage also physically communicates with the venturi chamber and is adapted to allow the expulsion of fluid out of the tool body in a radial or near radial direction.
Preferably, the tool further includes means for providing a third liquid passage and a filter means, wherein the third liquid passage is adapted to direct the flow of well fluid located in an annulus or space between the tool body and the well casing or well head toward and subsequently through said filter means.
Typically, the tool body is shaped and sized such that it is provided with a stepped outer profile which corresponds to the internal diameters of a well head, but so as to leave a space between the outer circumference of the tool body and the internal surface of the well head, wherein the space provides at least part of said third fluid passage.
The tool may include or be associated with a seal or barrier that prevents the flow of well fluid in the third fluid passage from bypassing the filter means.
The filter means may be provided in the form of a conventional junk basket. Alternatively, the filter means may be a screen.
Preferably, the inlet associated with the second fluid passage is positioned so as to only receive fluid that has been filtered through said filter means.
The discharge passage may also be provided with or associated with a further outlet, the further outlet being provided to allow well fluid to be circulated above the tool to surface.
Typically, the first fluid passage would incorporate a nozzle for creating a venturi in the vicinity of the venturi chamber.
The radial or near radial outlets associated with the discharge passage may also be provided with respective nozzles in order to provide for the jetting of fluid with appropriate velocity or force.
Preferably the radial outlets are adapted to direct the expelled fluid in a direction between the radial and axial axes, wherein the direction is chosen to optimise the ability of the expelled fluid to access or penetrate the various recesses in the well head or casing.
There may be two outlets positioned to work in tandem on a recess provided in the well head, wherein each outlet is adapted to expel fluid in a different direction from the other.